The present invention relates to suspension joint bearings, and in particular, to an improved suspension joint bearing having non-uniform lubrication and stress-relief slots disposed in optimized locations about a circumference thereof to permit axial movement and simultaneous radial lock-up within a bearing housing.
Conventional suspension joints, and other movable sockets are used, for example, in automotive steering and suspension applications. The sockets comprise a housing having a circular cylindrical or conical internal surface, a ball stud with a stud head contained in the housing, and one or more bearing members supporting the stud head within the housing. Traditionally, the bearing members are composed of a synthetic resin or sintered alloy. These components are installed into the housing through an opening, with the stud extending outward through an axially disposed opening which may either be the same opening through which the components were installed, or an axially opposite opening.
Traditionally, if two openings are present in the housing, one opening is closed by means of a cover-plate, spun, swaged, or welded in place. Once secured in place, the cover-plate presses on the bearing members either directly or indirectly through a resilient rubber or elastic steel intermediate component. Alternatively, for housings having only a single opening, once the components are in place, and the ball stud is protruding from the opening, the peripheral edges of the opening are swagged or rolled to retain the components in place, while simultaneously permitting movement of the ball stud.
Conventional bearing components within the housing, against which the stud head or moveable component is rotated and/or articulated, perform best when the sliding surfaces are fully hardened, as it is better able to withstand the stresses and frictional wear associated with movement of the conventional bearing components. Bearing components in a movable socket are subjected to rotational, axial, and radial loads. Accordingly, the use of hardened materials greatly extends the useful life of the bearing components and the housing.
Once assembled, movable sockets may be utilized as load carrying members in numerous mechanical systems, including automotive vehicle suspension and steering systems. Movable sockets or ball-joints employed in these applications are subjected to various operating conditions, and may be required to carry substantial loads. When wear develops, the performance of the movable socket or ball-joint degrades and, in the case of automotive applications, may result in erratic steering or excessive looseness and play in the vehicle suspension system. Accordingly, it is desired to minimize internal wear in the movable sockets or suspension joints.
A conventional lower bearing in a suspension joint typically includes a number of equidistantly spaced radial slots of uniform depth. These slots are intended to provide a limited degree of flexibility in the bearing, and to provide channels for the flow of lubricant to the bearing surfaces in the suspension joint, reducing internal wear and extending the operational life of the suspension joint. This configuration of radial slots either has a very high stress associated with the radial slots, or a very high stiffness. If the bearing has a high stress associated with the radial slots, the bearing may break during the process of assembling the suspension joint or during subsequent operation thereof. If the bearing has a high stiffness, two possible problems may arise. First, if the outer radial dimension of the bearing is greater than the inner radial dimension of the housing in which it is seated, the bearing may be difficult to fit within the housing during assembly. Once assembled in the housing, the bearing may become “locked” against movement in the suspension joint axial direction, rendering other axial compliance members, such as Belleville washers, disposed within the housing non-functional. Alternatively, if the outer radial dimension of the bearing is smaller than the inner radial dimension of the housing, the bearing will be loose within the housing in a radial direction. A loose bearing will rotate within the housing during service and create impact forces in the housing, greatly decreasing the useful life of the suspension joint.
Accordingly, it is desirable to provide an improved socket lower bearing which retains the functionality of providing flexibility in a radial direction, delivering lubricant to the bearing surfaces, but which is minimally stressed, and which is configured to remain “locked” against rotational movement direction while simultaneously permitting movement in an axial direction.